1. Field of the Invention
This invention relates to a door-lock mounting plate for use notably as an ornamental device in private houses.
The function of door-lock mounting intended for ornamental purposes is well known; they are also effective for protecting painted and other doors against finger marks.
2. The Prior Art
The plate style should in principle match the style of the door handle so as to be in harmony therewith. A hole is formed through the door plate for the square-sectioned handle-bar connecting the handle to the lock mechanism fitted in the door mortise.
Rotating the handle will actuate the bolt which recedes into the lock and thus permits the door opening movement. A door-lock comprises as a rule two springs, a first spring engaging the bolt directly for urging it to its operative or locking position. This spring is actuated alone when the door is slammed, without actuating the handle. Thus, it allows the bolt to recede into the lock simply when it is depressed by an external pressure.
The second spring incorporated in the lock urges the handle-bar to return the handle to its normal or inoperative position when no other external forces are exerted thereon. This second spring permits notably of preventing the handle from rotating when the bolt alone is actuated.
There are two main types of door handles, that is to say, the handles having a perfectly symmetrical configuration, such as the knob or ball type, and those which, in contrast thereto, are unbalanced by the presence of a lateral or overhanging arm.
Symmetrical handles are substantially trouble-free in operation. However, asymmetric handles, which are more widely used, are characterised by construction by a relatively considerable degree of unbalance. Thus, for instance, certain replicas of old-style door handles are made of solid metal, and therefore have an appreciable overhang.
This type of door handle exerts a considerable stress on the lock return spring and therefore after a relatively short time the presence of a heavy asymmetric handle and the excessive torque resulting therefrom are sufficient for preventing the bolt from moving outwardly so that the door cannot close and remain safely locked.
Nowadays the manufacture of locks is greatly standardized and programmed to meet all practical requirements with a relatively light handle. Any excess in this respect is attended by a premature damage of the lock.